1. Technical Field
The present invention relates to a profile creation method, a non-transitory computer readable recording medium stored with a profile creation program, and a profile creating apparatus, for creating a color conversion profile.
2. Description of Related Art
With the progress in developing desktop publishing (DTP) technology and the like, the use of digital printing for producing prints directly from print data by using an electrophotographic or ink-jet image forming apparatus has been more and more increasing.
Such image forming apparatus generally have limitation of the total use amount of color material such as toner or ink, in consideration of an issue of electrostatic properties and fixing performance at the time of image formation as for electrophotographic image forming apparatus, and an issue of drying properties of ink and absorbency of ink into recording paper as for ink-jet image forming apparatus.
Even for the image forming apparatus with limitation of the total use amount of color material, it is desired to produce accurate output colors of the image forming apparatus. Hence, controlling the color reproducibility of such an image forming apparatus by creating a color profile for color correction is beneficial.
There are mainly two methods of creating a color profile for an image forming apparatus with limitation of the total use amount of color material. The first method includes: outputting color charts without limiting the total use amount of color material or under a similar condition; measuring color values on the charts; and then creating a color profile which gives an output with limitation of the total use amount of color material (e.g., Japanese Patent Application Laid-Open No. 2010-130485). The second method includes: outputting color charts with limitation of the total use amount of color material; measuring color values on the charts; and then creating a color profile without taking into account limitation of the total use amount of color material.
It is easier to employ the second method than the first method, since the first method cannot be used for an image forming apparatus which is not capable of outputting color charts without limiting the total use amount of color material. However, the second method has a problem of causing a large interpolation error at the time of interpolating lattice points in a look-up table obtained by measuring color values on color charts since the amount of color material which is used at the time of outputting the color charts is changed by the process for limiting the total use amount of color material.
In the image forming apparatus with limitation of the total use amount of color material, a certain amount is set as a set amount at which the total use amount of color material is started to be limited, and a process for gradually reducing CMYK values having the total use amount of color material exceeding the set amount is performed, in order to maintain as much as possible smooth progression of pixel values before and after limitation of the total use amount of color material is imposed. For this reason, it is desired to create a color profile which enables printing with accurate color reproduction by accurately interpolating lattice points in a look-up table, for an image forming apparatus which selectively performs, on CMYK values having the total use amount of color material exceeding the set amount, the process for reducing the total use amount of color material.